At present, liquid crystal devices (LCDs) are commercially available as flat panel displays. Such liquid crystal devices employ paraelectric liquid crystal materials in a nematic phase with no macroscopic spontaneous polarization. Since nematic liquid crystals have potent fluid characteristics, they are highly stable against impact but have a response speed as low as about 10 msec. For these reasons, nematic liquid crystals do not rapidly respond to changes in electric field and the alignment of liquid crystal molecules becomes stable after a certain time, causing the problems of afterimages and image trails. Many proposals have been made on liquid crystal materials and driving modes capable of solving the problem of afterimages.
For example, since the 1980's, a number of studies have been devoted to ferroelectric liquid crystal devices which align chiral liquid crystal molecules in a particular direction using a surface alignment agent to induce macroscopic spontaneous polarization. Macroscopic spontaneous polarization induced in ferroelectric liquid crystals linearly interacts with an applied electric field, thereby advantageously enabling the ferroelectric liquid crystals to have a response speed of almost 1,000 times higher than that of nematic liquid crystals even at low voltages. Ferroelectric liquid crystals, however, have the disadvantage of poor impact resistance due to their high crystallinity.
Accordingly, liquid crystal devices having both the advantage of ferroelectric liquid crystals, i.e. high polarity, and the advantage of nematic liquid crystals, i.e. superior stability against impact, will contribute to solving the technical problems encountered with currently available LCDs. In this connection, since the late 1990's, the possibility of the existence of polar nematic liquid crystals having macroscopic spontaneous polarization and no positional ordering has been theoretically anticipated in the art [L. M. Blinov, Liquid Crystals, 24 (1998) 143]. Until now, however, no experimental results proving the existence of polar nematic liquid crystals have been reported by any research group throughout the world.
On the other hand, fabrication of conventional LCDs essentially involves treatment of substrates with aligners to uniformly align liquid crystal molecules. Materials for the aligners as well as equipment, time and cost required for additional surface coating, baking and rubbing cause an increase in fabrication costs and a reduction in fabrication yield. In addition, deterioration in quality, such as color purity and transmittance, due to inherent colors of aligners is caused and is thus a major obstacle in the fabrication of LCDs. Under these circumstances, there has been much research aimed to solve the above problems.
As a representative example, research has been conducted on photo-alignment using photoisomerizing materials since the 1990's. However, since there is no photoisomerizing material having sufficient surface anchoring force, photo-alignment still suffers from difficulty in practical use. Apart from the photo-alignment, techniques using inherent alignment characteristics on a specially-treated surface or self-assembly of basic units, such as ionic bonds, have recently drawn a great deal of attention. Since these techniques are disadvantageous over conventional techniques using aligners, in terms of high fabrication costs and poor basic characteristics, e.g., transmittance, only fundamental studies on the possibility of practical application are currently being conducted.